AU785408B2 - Apparatus for detecting operation of an electric fence - Google Patents

Description

DH Ref: 116-106AU DLH:MM

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Tru-Test Limited, 25 Carbine Road, Mount Wellington, Auckland New Zealand ANTHONY R. CARSON and KEIT Q. LAM of 215 S. Church, Waynoka, Oklahoma 73860, United States of America and 103 Lincoln, Waynoka, Okloahoma 73860, United States of America respectively.

Don Hopkins Associates Spruson Ferguson, Patent Attorneys Level 33, St Martins Tower, 31 Market Street Sydney, New South Wales 2000, Australia APPARATUS FOR DETECTING OPERATION OF AN ELECTRIC FENCE The following statement is a full description of this invention, including the best method of performing it known to me/us:- BACKGROUND OF THE INVENTION i. Field of the Invention The invention relates generally to apparatus for detection of the proper function of an electric fence and/or a fence energiser connected to the fence. More particularly, the invention relates to a compact and durable sensing device which can be readily mounted onto or near an electric fence for detecting proper operation of the fence and of an energiser 2. Description of the Prior Art The imposition of a voltage on fencing intended to .o maintain livestock within a specified area has become well known as an alternative or addition to the fencing of livestock or the like by means of conventional fencing intended to retain such stock by virtue of the strength of the fencing rather than by an electrical shock which causes the stock to avoid the fencing. An appropriate voltage is applied by means of the fence energiser which typically applies a pulsed output to at least one electrical conductor comprising the fencing. Examples of presently available electric fence energisers include the random pulse charging apparatus of Phillips et al which SPEC1283 20 FEBRUARY 2001 is disclosed in United States patent 4,316,232.

McKissack, in United States patent 4,859,869, discloses the use of transformers for continuous energization of an electric fence. Standing, in United States patents 4,394,583 and 4,691,084, described electrical fence energisers as does Shaw et al in United States patent 5,381,298.

While electric fence and fence energiser combinations usually provide satisfactory operation, certain circumstances can occur whereby a fence does not function or function correctly either by failure of the fence energiser or by damage to the fence itself such as by cutting of the fence or other circumstance which causes 15 an open circuit or "short" condition. While fence energisers may employ visual or audible signals on the apparatus itself to indicate failure or incipient failure oeooe S"of the fence energiser, it is not possible to determine these conditions unless personnel are deployed in the area of the fence energisers per se in order to detect such indications. Accordingly, a need has been felt in the art to provide a simple and inexpensive means by which an observer at essentially any location along an electric fence can be informed of the operational state of the electric fence so that a determination can be made in the event of an indicated failure as to whether a SPEC1283AU 21 FEBRUARY 2001 failure of the fence energiser exists or whether conductive elements of the electric fence have been breached such as by cutting or other separation thus causing an open or short circuit.

The art has previously provided monitoring and alarm systems used in association with electric fences and fence energisers. Begg, in United States patent 4,523,187 provides one such alarm while Pope et al, in United States patent 4,220,949, provides a fence monitor as does Hamm in U.S. patent 5,550,530. McCutchan et al, in United States patent 4,297,633 provides remote devices on electric fence sections whereby the devices transmit signals to a central control location.

ooooe S. SAlthough the art has provided monitoring and alarm systems such as are represented by the United States oooo•: patents cited herein, the art continues to feel the need for a compact and inexpensive device which can be placed 20 on a conductive element of an electric fence and which provides a signal, particularly a visual signal in the form of a flashing light, in the event of the inability of a fence energiser to maintain an output voltage on the fence or the lack of an output voltage on any portion of the fence such as can occur due to heavy vegetation loading that portion of the fence or a separation of at SPEC1283AU 21 FEBRUARY 2001 least one of the electrical conductors of the fence such as by cutting or any separation of electrical conductors or collapse of any portion of the fence causing an open or short circuit.

The present invention has as its object a compact, inexpensive and durable apparatus for sensing the operational state of an electric fence and/or the electric fence energiser connected to the fence.

SUMMARY OF THE INVENTION Broadly according to one aspect of the invention there is provided an apparatus for sensing the operational state e: i 15 of an electrical fence and/or fence energiser electrically connected to the fence the apparatus e• including a housing, a power supply and an indicator, a .oloei first circuit carried by the housing for sensing the electric field of at least a portion of the electric fence, the circuit being ungrounded to earth and a second circuit operable by the first circuit on reduction of the electric field for operating the power supply to drive the indicator and thereby indicate a malfunction of the fence and/or the fence energiser.

SPEC1283AU 21 FEBRUARY 2001 22/02 2007 14:26 FAX 64 6 3590198 DON HOPKINS 4 IP AUST SECURE 01005 o o Broadly according to a second aspect of the invention there is provided apparatus for sensing the operational state of an electric fence and/or a fence energiser electrically connected to the fence, comprising; a housing, power supply means and, circuit means for sensing the electric field of at least a portion of the electric fence, the circuit means being ungrounded to earth, an input of the circuit means being connected to electrically conductive means which forms at least a portion of the electric fence and indicator means operable by said circuit means upon the circuit means sensing a reduction of the electric field across the apparatus indicating a malfunction of the fence and/or the fence energiser.

SPEC1283AU 20 FEBRUARY 2001

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COMS ID No: SBMI-06347674 Received by IP Australia: Time 12:23 Date 2007-02-22 The invention provides a compact, inexpensive and exceptionally durable device which can be simply attached at a multiplicity of locations on or in close proximity to a conductive portion of an electric fence with contact thus being provided between the fence and circuitry internal of the device, any desired number of the present devices being usable without drawing down voltage.

The device of the invention in its several embodiments includes a self-contained power source such as batteries of appropriate size and voltage, a circuit board carrying circuitry elements, a source of illumination disposed within the device and a shock-resistant "plastic" lens which forms at least a part of a housing within which 15 components of the device are disposed and interrelated for appropriate function. The devices of the invention may be disposed at locations sufficiently close to 4 electrified wire fence conductors such that electric field is sensed even though the devices of the invention do not actually contact the electric fence wire/conductors.

Circuitry suitable to an appropriate operation of the invention can take a variety of forms according to the invention examples of which are disclosed herein.

SPEC1283AU 21 FEBRUARY 2001 6 That part of the circuitry causing communication with the electric fence and/or with the fence energiser can be a clip or other mounting arrangement which simply and readily fits over an electrical conductor of the electric fence at any location of the fence. Alternatively an electric potential sensing means such as an electrically conductive element housed within the device and positioned sufficiently close to an electrical conductor of the fence, the clip, other mounting arrangement or electric potential sensing means can be directly connected to circuitry internal of the device.

The circuitry causes operation of the device to provide S.an appropriate visual signal in the event of the failure 15 of the fence to exhibit an appropriate charge or the failure of the fence energiser to appropriately apply to desired voltage to the fence. The circuitry can also S" sense when voltage drops below a predetermined value and provide a signal indication of such a voltage drop.

A particularly useful circuit defined according to the invention includes an integrated circuit as a part of the circuitry providing control, an output from the integrated circuit causing a transistor to oscillate, oscillation of the transistor controlling a light source carried by the device. It should be understood that the SPEC1283AU 21 FEBRUARY 2001 light source is preferably carried within the device in order to prevent damage to the light source.

In this preferred circuit, the integrated circuit functions essentially as a timer and further provides means for adopting other functions to the circuitry as desired. For example, self-test functions or the like can be incorporated into the preferred circuitry due to the presence within the circuitry of the integrated circuit comprising the timer function. In a similar vein, auxiliary subsystems can be connected into the circuitry through the integrated circuit to provide other functions without any real modification of the original circuit.

The invention further contemplates provision of a control and/or timing function by means of the operation of "discrete circuit elements including at least one resistor and at least one transistor which function to control the 20 oscillation of a transistor and thus control of the light source. It is to be understood that the light source in the several embodiments of the invention can take several forms including low voltage DC lamps of the incandescent types as well as light emitting diodes of various description, it being desirable to utilize light emitting diodes having the capability of flashing operation.

SPEC1283AU 21 FEBRUARY 2001 8 In the several embodiments of the present circuitry, it is to be noted that the circuitry is not grounded to earth ground, be it represented by earth return wires and/or earth in the vicinity of the device's location, and that the electrical reference is at the battery negative terminal. As can be appreciated, electrical reference could also be to the battery positive terminal or any other point in the circuit that is at a nominally fixed voltage with respect to the battery negative terminal, according to well-known electrical principles.

Accordingly, it is thus seen that the impedance of air between the device's circuitry and earth ground and in at ooooo 5 least one embodiment also to the fence conductor is used to prevent lowering of the voltage of the fence energiser and also to provide one or two large series impedances in •coco: a potential divider wherein a second or third series impedance is provided at the input of the device's circuitry.

The invention in its several embodiments will be seen to be compatible with all types of fence energisers whether pulsed or continuous. The present devices function within a wide range of temperatures and within a wide range of weather conditions. The devices of the SPEC1283AU 21 FEBRUARY 2001 invention further will not drop the voltage of the fence energiser, a clip connecting the device to the fence or an electric potential sensing means such as an electrically conductive element housed within the device and positioned sufficiently close to an electrical conductor of the fence further connecting directly to circuitry within the device and providing input from the fence energiser to such circuitry. The clip provides a means for hanging the devices of the invention on a high voltage fence wire without danger of shock.

The illumination source of the several devices of the invention only flashes when a fence energiser is not working properly or when the fence voltage at the 5 location of the device is below a predetermined threshold, such as occurs when the fence has an open or short circuit.

Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an idealised perspective view illustrating a detection device configured according to the invention SPEC1283AU 21 FEBRUARY 2001 and including a housing carrying a power source, an illumination source, controlling circuitry and a clip or similar mechanism for hanging the assembly to a portion of an electric fence in order to effectively communicate the condition of the fence and of a fence energiser connected to the fence to circuitry contained within the apparatus of the invention; FIGURE 2 is a circuit diagram illustrating a preferred embodiment of the circuitry of the invention; and FIGURE 3 is a block diagram illustrating an alternative circuit which can be used in the device of Figure 1.

15 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and particularly to Figure a detector configured according to the invention is seen generally at 10 to comprise a housing 12 formed of a lens element 14 and a back plate 16. A power source such as batteries 18 is mounted in any convenient fashion to ~.an inner surface of the back plate 16, the back plate 16 then being mounted either directly to the lens element 14 or to a rear housing element 17 in any convenient fashion. For example, the back plate 16 can be provided with screw threads (not shown) which mate with threads SPEC!283AU 21 FEBRUARY 2001 11 formed about an opening in the element 17 so that the back plate 16 can be conveniently and positively attached to the housing 12. The lens element 14 and the rear housing element 17 can be permanently attached to each other or can be integrally formed, it only being necessary for the lens element 14 to be formed of a clear, "plastic" material having sufficient durability to withstand the rigors of the outdoor environment within which the detector 10 is intended to function.

Interiorly of the housing 12 and in a position to direct light through the lens element 14 is disposed a light source 22, the operation of which is controlled by circuitry 26 mounted on a circuit board 20, the circuit 15 board 20 being mounted in any convenient fashion within the interior of the housing 12. It is to be understood that reflector elements can be provided within the eoooo S"interior of the housing in order to efficiently reflect light through the lens element 14. Further, the lens element 14 can preferably be formed of a material having a color tint which would cause illumination of the light ee.o source 22, especially flashing illumination, to be more readily observed. In practice, an amber light emitting diode coupled with yellow reflective materials or yellowtinted materials is preferred.

SPEC1283AU 21 FEBRUARY 2001 12 A connector 24 is mounted to the housing 12 and has conductive elements (not shown) which extend into electrical contact with the circuitry 26 mounted on the circuit board 20. Electrical connection between this connector 24 and the circuitry 26 is illustrated in Figures 2 and 3.

The connector 24 not only provides a mechanism by which the detector 10 can be mounted to, that is, "hung" onto an electrically conductive fence element (not shown in Figure the connector 24 also couples the circuitry 26 of the detector 10 to an electrically conductive fence element and therefore a fence energiser (shown in Figures 2 and 3) without providing a shock risk. In particular, S: 15 the circuitry 26 of the detector 10 is not grounded to earth ground, the electrical reference of the detector thus preferably being at the negative terminal of the battery or batteries 18. Accordingly, the impedance of the air in the vicinity of the hanging connection and between the detector 10 and earth ground acts to prevent lowering of the voltage of the fence energiser. This grounding of the detector 10 to the negative terminal of lo *0 the battery 18 rather than to earth ground means that any number of the detectors 10 can be hung onto an electric fence without drawing down voltage on the fence, thereby allowing detection of the operational state of the fence SPEC1283AU 21 FEBRUARY 2001 13 energiser 30 and of the fence at any desired number of locations by any desired number of detectors 10 at any given time. Further, a drop in voltage on the fence to a predetermined degree, such as to 1000 volts, can be detected by the detector 10 with a resulting visual indication being provided by said detector.

From the foregoing, it is apparent that the detector need not be hung directly on an electrically conductive fence element. The detector 10 can be mounted to a fence post or the like in juxtaposition to an electrically conductive fence element such that the electric field between the fence element and earth ground, be it represented by earth return wires and/or earth in the S 15 vicinity of the device's location, is sensed.

Accordingly, an electrically conductive wire of an electric fence does not have to be touched by any portion S"of the circuitry in detector 10 as long as the detector is close enough to the charged wire in order to detect a flux signal which radiates from the wire with sufficient amplitude to charge the requisite capacitor of *foe 0. the sensing circuit. An impedance in the form of a capacitor and resistor in parallel can separate a sensing circuit of the detector 10 from a charged wire in a manner similar to the separation provided by the air gap.

In essence, air in the vicinity of the connection acts as SPEC1283AU 21 FEBRUARY 2001 14 an impedance, just as air between the detector 10 and ground forms an impedance the function of which contributes substantially to the desirable operation of the detector A consideration of the structure of the detector 10 as seen in Figure 1 reveals alternatives as to the construction thereof. For example, a light emitting diode can be utilised as the light source 22 and particularly a light emitting diode capable of flashing operation. While a DC-driven light source such as an incandescent bulb can be utilised, power drain on the batteries 18 will be substantially reduced through use of a light emitting diode as the light source 22. The light 0r 15 source 22 is connected into the circuitry 26 in a manner 00 00 *as is disclosed in the discussion of Figures 2 and 3 as provided hereinafter. It is further to be understood S"that the batteries 18 could take the form of disc-type 0000 batteries which could be mounted within circular 20 depressions formed in the back plate 16, for example.

Such batteries are usually slotted to allow removal from :.:00 circular depressions which are threaded to mate with threads formed on the batteries themselves.

Referring now to Figure 2, a preferred circuit is shown.

The circuit 26 of Figure 2 includes a light emitting SPEC1283AU 21 FEBRUARY 2001 diode 48 having flashing capability as the light source 22. The batteries 18 of Figure 1 are seen to also be a part of the circuit 26 and are described as battery 55 in the circuitry of Figure 2.

Figure 2 illustrates an electrically conductive fence element 28 in schematic fashion, such a fence element 28 being typically formed of wire and being that portion of an electric fence on which the connector 24 is hung in order to mount the detector 10 to the electric fence.

The fence element 28 is shown in a schematic fashion to be connected to a fence energiser 30 which may essentially comprise a energiser of any known type whether continuous or pulsed and within the usual output ooooe 15 voltage ranges of such energisers.

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When the fence energiser 30 is operable to apply an S° output voltage to the fence element 28 on which the e g.

detector 10 is mounted through the connector 24, .o 20 resistors 32 and 34 sense the voltage provided by the fence energiser 30. The fence energiser 30 causes a small current to be fed from junction 33 of the resistors 32 and 34, this current flowing to the base of transistor 36 and thereby turning the transistor 36 on. Activation of the transistor 36 charges capacitor 38 with a resultant activation of the transistor SPEC1283AU 21 FEBRUARY 2001 When the transistor 40 is thus activated or caused to be in an "on" condition, capacitor 42 is discharged through the transistor 40, thus causing output of timer 44 to go "high". When the output of the timer 44 goes high, transistor 46 turns off and the light source in the form of the light emitting diode 48 is also "off".

Accordingly, in the condition whereby the fence energiser 30 is properly operating, and the fence is in good condition, the detector 10 senses the charge imposed upon the fence element 28. It thus senses that the fence energiser 30 is performing properly and the fence is in a good condition such that a voltage exists as is expected on the fence element 28. In this condition, the light source, that is, the light emitting diode 48, is o inoperative.

In the condition whereby the fence energiser is in the 20 "off" condition for any reason such as by actual failure, *e the charge in the capacitor 38 slowly drops to zero volts, thus preventing the capacitor 42 from being S"discharged. It is thus seen that the capacitor 42 charges through resistor 50 and resistor 52, a network 54 being essentially formed by the resistors 50, 52 and the capacitor 42. Once the capacitor 42 has charged up to SPEC1283AU 21 FEBRUARY 2001 17 approximately two-thirds of the supply voltage, the output of the timer 44 will go "low" and the capacitor 42 will slowly discharge through resistor 52. When the capacitor 42 is discharged below approximately one-third of the supply voltage, the output of the timer 44 will go "high" and the capacitor 42 will be recharged again.

This charge/recharge cycle of the capacitor 42 causes the timer 44 to oscillate the transistor 46 since the gate of the transistor 46 is controlled by the output of the timer 44. The rate of the oscillation is determined by the product of the resistor 50, the resistor 52 and the capacitor 42 which form the network 54 as indicated *."*previously. The light source, that is, the light emitting diode 48, is controlled by the oscillation of the transistor 46.

Accordingly, failure of the fence energiser to maintain the appropriate voltage on the fence element 28 causes 20 the light emitting diode 48 to flash and thus provide a .e visual failure indication. The detector 10 thus only provides a visual failure indication when the fence S"energiser 30 is not working properly or when the electric fence voltage at the location of the device is below a predetermined threshold, such as occurs when the fence has an open or short circuit such as can be caused by SPEC1283AU 21 FEBRUARY 2001 18 cutting of the fence or by a separation occurring due to the other causes.

Referring again to Figure 2, it is seen that the timer 44 takes the form of an integrated circuit, the output of which at 3 controlling the gate of the transistor 46 to thereby oscillate the transistor 46. The integrated circuit comprising the timer 44 provides flexibility to the circuit of Figure 2 when considered relative to discrete element circuitry since options can be connected to the circuit through the integrated circuit comprising the timer 44 with minimum or no modification to the circuit. Such modifications can include circuit subsystems providing other alarm indicators, self-test functions, etc.

The integrated circuit of the circuit of Figure 2, that is, the timer 44, can be provided with GND at 1, a TRIGGER function at 2, and OUTPUT function at 3, a RESET 20 function at 4, a THRESHOLD function at 6, a DISCHARGE function at 7 and a VCC function at 8. A control function could be provided at a position such as the .e S"position (not shown). The circuit can otherwise be provided with conventional discrete circuit elements.

However, it is to be understood that the resistors can preferably be carbon film of 1/8 watt.

SPEC1283AU 21 FEBRUARY 2001 19 The light emitting diode 48 should preferably have high efficiency and intensity. Further, all transistors should preferably have a gain of a minimum of 200 while the integrated circuit taking the form of the timer 44 is preferably of the CMOS type. The resistor 50 should preferably be between 1M and 2M for flash rate setting.

All electrical components can be surface mounted or through-hole mounted on the circuit board 20. The detector 10 functions maximally with all types of fence energisers and especially where pulses are less than Hz or once every two seconds. The flash rate of the detector 10 is approximately once every three seconds.

It is further to be noted that the transistors 36 and are NPN type transistors while the transistor 46 is a PNP transistor. The capacitors are typically 1 microfarad, 15 V electrolytic devices. The integrated circuit, that is, the timer 44, is chosen to be a TC 555 CMOS timer.

e Referring now to Figure 3, an alternative circuit is shown and comprises a number of discrete circuitry elements which are present in the circuit of Figure 2, these elements functioning in essentially the same manner. However, the timer 44 has a transistor 56 and a resistor 58 substituted therefor.

SPEC1283AU 21 FEBRUARY 2001 In operation, the resistors 32 and 34 sense voltage when the fence energiser 30 is operating appropriately, the fence energiser 30 feeding a small current from the junction 33 of the resistors 32, 34, this current flowing to the base of the transistor 36 with the result that the transistor 36 is turned on. The capacitor 38 is charged through the transistor 36 and turns on the transistor When the transistor 40 is in the "on" condition, the capacitor 42 is discharged through the transistor causing the transistor 56 to turn off, the transistor 46 also being caused to turn off so that the light emitting diode 48 is also off.

When the fence energiser 30 is not functioning, the *charge in the capacitor 38 slowly drops to zero volts S-thus preventing the capacitor 42 from being discharged.

As with the circuit of Figure 2, the capacitor 42 charges through the resistors 50 and 52. When the capacitor 42 20 has charged up to a voltage causing the transistor 56 to ee turn on, the transistor 56 simultaneously turns the transistor 46 on, thus causing the light emitting diode 48 to flash. The flash rate of the light emitting diode 48 is determined by the inherent rate of the LED itself.

SPEC1283AU 21 FEBRUARY 2001 As is the case with the circuit of Figure 2, the circuit of Figure 3 is not grounded to earth ground, the electrical reference being at the negative terminal of the battery 55. Accordingly, the impedance of the air functions to prevent lowering of the voltage of the fence energiser 30. The transistor 46 of the circuit of Figure 3, is an NPN transistor rather than the PNP transistor of the circuit of Figure 2.

While the detector 10 including the circuits 26 and 57 have been described as explicit embodiments of the inventive concept disclosed herein, it is to be understood that the conformation of the detector 10 and particular circuit elements can be configured other than 5 as explicitly shown and described herein without departing from the scope of the invention as defined by the appended claims.

oeoeo: *e SPEC1283AU 21 FEBRUARY 2001

Claims (5)

1. 3. Apparatus as claimed in claim 2 wherein, said ~electric potential sensing means is adapted to be disposed sufficiently close to but not touching the electric fence to allow sensing of the electric field. SPECI283AU 21 FEBRUARY 2001
2. 4. Apparatus as claimed in claim 1, 2 or 3 wherein the electrical reference is to a negative terminal of the power supply or any point in the circuit. Apparatus as claimed in claim 2 or 3 wherein the means electrically connected to the first circuit comprise an electrically conductive clip for engaging the portion of the electric fence. 6 Apparatus as claimed in any one of the preceding claims wherein the first circuit includes sensing means for sensing a potential difference above a predetermined level is present at the input of the first circuit; the first circuit further comprising switching means for disconnecting the power supply from the indicator while the potential difference sensed by the sensing means 20 is above the predetermined level. 7 Apparatus as claimed in any one of the preceding claims wherein the power supply includes a battery. SPEC1283AU 21 FEBRUARY 2001 24 8 Apparatus as claimed in any one of the preceding claims wherein the indicator includes a light emitting diode 9 Apparatus as claimed in any one of the preceding claims wherein the second circuit comprises an indicator driving circuit which is disabled by the switching means while *the potential is in difference sensed by the sensing means is above a predetermined level the on condition, the indicator driving circuit being enabled by the switching means when the potential difference sensed by the sensing means falls below the predetermined level, the indicator driving 1 5 circuit becoming operable to drive the indicator in a flashing manner, denoted by the indicator driving circuit to indicate a malfunction of the electric fence and/or the fence energiser. oooeo: 10 Apparatus as claimed in claim 9 wherein at least a portion of the housing is formed of a light .transmissive material to allow the indicator to be visible from externally of the housing.
3. 11. Apparatus for sensing the operational state of an electrical fence and/or fence energiser SPEC1283AU 21 FEBRUARY 2001 22/02 2007 14:27 FAX 64 6 3590198 DON HOPKINS 4 IP AUST SECURE I0o06 electrically connected to the fence, the apparatus including a housing, a power supply and an indicator, a first circuit carried by the housing for sensing the electric field of at least a portion of the electric fence, the circuit being ungrounded to earth.
4. 12. Apparatus as claimed in claim 11 further including a second circuit operable by the first Scircuit on reduction of the electric field for operating the power supply to drive the indicator and thereby to indicate a malfunction of the fence and/or the fence energiser.
5. 13. Apparatus for sensing the operational state of an electric fence and/or a fence energiser electrically connected to the fence, comprising; a housing, power supply means and, circuit means 20 for sensing the electric field of at least a portion of the electric fence, the circuit means being ungrounded to earth, an input of the circuit means being connected to electrically conductive means which forms at least a portion of the electric fence and indicator means operable by said circuit means upon the circuit SPEC1283AU 20 FEBRUARY 2001 COMS ID No: SBMI-06347674 Received by IP Australia: Time 12:23 Date 2007-02-22 22/02 2007 14:27 FAX 64 6 3590198 DON HOPKINS IP AUST SECURE 0007 26 means sensing a reduction of the electric field across the apparatus indicating a malfunction of the fence and/or the fence energiser. 14 Apparatus as claimed in any one of claims 1 to 13 further including a lens element forming a portion of the housing, the lens element allowing light from a light source forming said indicator means to pass externally of the housing. Apparatus as claimed in cli 1 wherein the lens element is formed of a clear, color-tinted S: material. 16 Apparatus for sensing the operational state of an *electric fence and/or fence energiser electrically connected to the fence substantially 0 as herein described with reference to the accompanying drawings. DATED this 2 1 st day of February 2001 TRU-TEST LIMITED Patent Attorneys of the Applicant/Nominated Person DON HOPKINS ASSOCIATES SPEC1283AU 21 FEBRUARY 2001 SPEC L3AU COMS ID No: SBMI-06347674 Received by IP Australia: Time 12:23 Date 2007-02-22